System and method for storing crankcase gases to improve engine air-fuel control

ABSTRACT

A system and method for improving processing of gases contained within the crankcase of an internal combustion engine is presented. The system is especially suited for single boiling point fuels because it allows the storage of such fuels until the fuel can be opportunistically combusted.

FIELD

The present description relates to a system and method for combustinginternal combustion engine crankcase gases.

BACKGROUND

A system and method for operating an internal combustion engine usingpositive crankcase ventilation (PCV) is described in U.S. Pat. No.6,729,316. The patent describes a system wherein emissions are pumpedfrom a crankcase to a canister. The canister contains a deceleration andcondensing element comprised of glass beads. It is believed that theglass beads decelerate flow originating from the crankcase and causehydrocarbons to condense so that they can be discharged to a collector.The canister purportedly separates contaminants from the crankcase andthen passes the cleansed emissions back to the engine for combustion.

The above-mentioned system can also have several disadvantages.Specifically, fuel vapors are sent to the engine shortly after beingprocessed through the canister. If the crankcase gases are related to asingle boiling point fuel (e.g., alcohol), much of the alcohol cantransition to the vapor state in a short period of time. As such,concentrated vapors can be drawn into the separating canister and thentransferred to the engine at a rate that causes the engine to run rich.Thus, the canister may extract contaminants from the crankcaseemissions, but the device does not appear to offer any means to controlthe rate that exhaust gases are transferred to the engine. Further, ifcrankcase gases cause the engine to operate rich, the engine controlleradaptive fuel strategy may cause the engine to operate lean after thecrankcase gases are purged from the engine. Thus, it does not appearthat the system improves engine air-fuel control when gasses are purgedfrom the engine crankcase.

The inventors herein have recognized the above-mentioned disadvantagesand have developed a system and method that offers substantialimprovements.

SUMMARY

One embodiment of the present description includes a system forcombusting internal combustion engine crankcase gases, the systemcomprising: an internal combustion engine comprising a crankcase, anintake manifold, a duct connecting the crankcase to the intake manifold,a canister comprising hydrocarbon storage media, the canister locatedalong the length of the duct and in communication with the duct, and anadjustable valve capable of regulating flow of gases from the crankcaseto the canister. This system overcomes at least some disadvantages ofthe above-mentioned system.

Venting gases from an engine's crankcase to the engine's intake systemmay be improved by trapping the gases before they are directed to theengine's intake system. A hydrocarbon trap can be installed in the pathbetween the crankcase and intake manifold to trap hydrocarbons as theymove from the crankcase toward the engine's intake system. The trap canbe used to control the rate at which hydrocarbons are introduced to theintake manifold. Specifically, an engine controller can use valves andpurge air temperature control to adjust the rate that hydrocarbons enterthe intake system. Further, the controller can make adjustments toengine fuel injection timing to compensate the controlled release ofhydrocarbons to the engine intake system. This system is particularlybeneficial when single boiling point fuels are vented from the enginecrankcase because the hydrocarbons can be stored during a short timeperiod and released over a longer time period.

The present description can provide several advantages. For example, thepresent system can reduce air-fuel excursions when crankcase gases arevented because the system can control hydrocarbon flow from the canisterand because it takes less time to compensate for small air-fuelvariations than for large air-fuel variations. Further, the system canstore high concentration hydrocarbons over a short period of time.Therefore, the system is suitable for processing single boiling pointfuels. Further still, the system can be controlled such that crankcasegases are stored during some engine operating conditions and releasedduring other operating conditions. Consequently, crankcase gases can becombusted more efficiently.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings,wherein:

FIG. 1 is a schematic diagram of an example engine having crankcaseventilation and its control system;

FIG. 2 is a flowchart of an example method for improving compensationfor crankcase ventilation; and

FIG. 3 is an example crankcase ventilation sequence.

DETAILED DESCRIPTION

Referring to FIG. 1, internal combustion engine 10, comprising aplurality of cylinders, one cylinder of which is shown in FIG. 1, iscontrolled by electronic engine controller 12. Engine 10 includescombustion chamber 30 and cylinder walls 32 with piston 36 positionedtherein and connected to crankshaft 31. Combustion chamber 30 is knowncommunicating with intake manifold 44 and exhaust manifold 48 viarespective intake valve 52 an exhaust valve 54.

Each intake and exhaust valve is operated by a mechanical camshaft 130that is rotated by coupling the camshaft to crankshaft 31. In analternative embodiment, one or more valves may be operated by electricalor hydraulic actuators.

Fresh air enters intake plenum 63 where its mass is determined by massair sensor 115. Most fresh air is routed into engine 10 throughelectrically controlled throttle 62 where it enters intake manifold 44.However, a portion of inducted air enters engine 10 through valve cover50 by way of duct 66. Air is drawn through duct 66 by a differentialpressure between intake manifold 44 and crankcase 51. Air goes from thecylinder head to crankcase 51 by way of passages that connect thecylinder head and the crankcase. As the air passes through the cylinderhead and crankcase, it mixes with and displaces fuel vapors inside theengine. Fuel vapors exit crankcase 51 and are routed through valve 71 tointake manifold 44 or through PCV canister 76. PCV Canister 76 maycontain carbon, zeolite, or an alternate form of hydrocarbon storagemedia. Fuel vapors can be purged from PVC canister 76 by opening valve72 and providing fresh air across the trapping media by way of optionalvalve 73. The fresh air may be heated by exhaust gas heat exchanger 46or by another means to increase the rate at which hydrocarbons arereleased from the trapping media. In an alternative embodiment, heatedcrankcase gases may be used to purge a canister of hydrocarbons byallowing crankcase gases to pass through valve 71 and valve 72 to intakemanifold 44.

In an alternative embodiment, PCV canister 76 may be sealed within theengine (e.g., under the valve cover or in the crankcase) so that thehydrocarbon storage media remains at an elevated temperature after theengine warms. Keeping the media temperature elevated may increase therate at which hydrocarbons can be purged from the storage media.

Intake manifold 44 provides a conduit for air to travel between throttle62 and intake valve 52. Fuel is directly injected to combustion chamber30 by way of injector 66. Fuel is delivered to fuel injector 66 by fuelsystem (not shown) including a fuel tank, fuel pump, and fuel rail (notshown). Alternatively, the engine may be configured such that the fuelis injected into a port of intake manifold 44, if desired.

Distributorless ignition system 88 provides ignition spark to combustionchamber 30 via spark plug 92 in response to controller 12. UniversalExhaust Gas Oxygen (UEGO) sensor 45 is shown coupled to exhaust manifold48 upstream of catalytic converter 49. Alternatively, a two-stateexhaust gas oxygen sensor may be substituted for UEGO sensor 45.

Converter 49 can include multiple catalyst bricks in one example. Inanother example, multiple emission control devices, each with multiplebricks, can be used. Converter 49 can be a three-way type catalyst inone example.

Controller 12 is shown in FIG. 1 as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, andread-only-memory 106, random-access-memory 108, 110 Keep-alive-memory,and a conventional data bus. Controller 12 is shown receiving varioussignals from sensors coupled to engine 10, in addition to those signalspreviously discussed, including: engine coolant temperature (ECT) fromtemperature sensor 112 coupled to water jacket 114; a throttle positionsensor 69; a cam position sensor 150; a position sensor 119 coupled to aaccelerator pedal; a measurement of engine manifold pressure (MAP) frompressure sensor 122 coupled to intake manifold 44; a measurement (ACT)of engine air amount temperature or manifold temperature fromtemperature sensor 117; and a engine position sensor from sensor 118sensing crankshaft 40 position. Sensor 118 may be a variable reluctance,Hall effect, optical, or magneto-resistive sensor. Alternatively, acamshaft position sensor may also be provided and may be used todetermine engine position. In a preferred aspect of the presentdescription, engine position sensor 118 produces a predetermined numberof equally spaced pulses every revolution of the crankshaft from whichengine speed (RPM) can be determined.

Storage medium read-only memory 106 can be programmed with computerreadable data representing instructions executable by processor 102 forperforming the methods described below as well as other variants thatare anticipated but not specifically listed.

In an alternative embodiment (not shown), engine 10 is a diesel enginewherein fuel is injected directly into a cylinder and combusted viacompression ignition. PCV canister 76 is positioned between crankcase 51and intake manifold 44. If desired, compressed air from a compressor canbe routed to PCV canister 76 such that throttle 62 is bypassed. Thecompressed air flows over the canister storage medium and stripshydrocarbons from the storage medium. The hydrocarbons are then directedinto the intake manifold by way of a control valve 72. This arrangementallows the canister to be purged even when the intake manifold is nearor higher than atmospheric pressure.

In yet another embodiment (also not shown), compressed air can bedirected through PCV canister 76 without bypassing throttle 62 byproviding valves that direct flow through the PCV canister and thenthrough throttle 62.

In still another embodiment, the PCV canister contents can be routed tothe inlet side of an inlet compressor so that the low pressure side ofthe compressor draws PCV canister vapors into the engine.

Referring now to FIG. 2, an example flowchart for improving crankcaseventilation compensation is shown. At step 201, engine operatingconditions are determined. Engine coolant temperature, time since start,ambient temperature, engine load, fuel injection amount, and exhaust gasoxygen concentration are inferred or sensed. However, additional orfewer engine operating parameters may be input from sensor data. Inaddition, some engine operating conditions determined from characterizeddata and from other sensed engine operating conditions. For example,engine exhaust gas temperature may be inferred from engine speed,cylinder air charge, and engine coolant temperature. After determiningengine operating conditions, the routine proceeds to step 203.

At step 203, the routine determines the type of fuel (e.g., gasoline,ethanol, mixtures of gasoline and ethanol, diesel, or natural gas) beinginjected to the engine. In one embodiment, fuel type for the presentengine start can be determined from information stored in the enginecontroller during the last period of time that the engine operated. Inother words, it can be assumed that the fuel combusted just prior to anengine stop is the substantially the same fuel used to start the engine.For example, fuel type can be inferred from the amount of fuel injected,the cylinder air amount, and the exhaust gas oxygen concentration.Specifically, fuel type can be inferred from the ratio of fuel to airthat produces a stoichiometric exhaust gas mixture. The stoichiometricair-fuel ratio can then be related to a specific fuel type. For example,when stoichiometric exhaust is detected at an air-fuel ratio of about9:1 the engine controller can infer that the type of fuel beingcombusted as ethanol.

Alternatively, a sensor in the fuel supply line may be used to determinethe type of fuel that will be combusted in the engine. Such a sensor mayassess fuel type by refraction, sensed capacitance, or other knownmethods. Similar to the method described above, sensor information thatindicates fuel type at engine stop can be used to determine and indicatefuel type at start. After the fuel type is determined the routineproceeds to step 205.

At step 205, the routine determines or estimates the amount of fuel inthe engine crankcase that can vaporize. In one embodiment, the routineuses engine temperature, the number of cylinder combustion events, typeof fuel, amount of fuel injected, crank angle at which fuel is injected,and the estimated amount of fuel in the crankcase at the last enginestop to estimate the amount of fuel presently in the crankcase. Theroutine also has the capacity to determine the entire mass of fuel inthe crankcase as well as the individual fuel masses that make up thetotal estimated crankcase fuel mass.

In one embodiment, the routine estimates that a fraction of the totalamount of fuel injected to a cylinder during a combustion cycle thatends up in the crankcase. Engine temperature, type of fuel injected, andcrankshaft angle at which injection occurs are used to look-upempirically determined factors that when added together represent thefractional amount of a cylinder's fuel charge that ends up in thecrankcase. This fractional amount is multiplied by the amount of fuelinjected into a cylinder to determine an amount of fuel that entered thecrankcase during a particular combustion event. The fuel type (i.e., thefractional concentrations of gasoline and alcohol) determined in step203 are multiplied by the total estimated mass of fuel entering thecrankcase. In this way, the masses of the individual fuel componentsentering the crankcase can be determined. The total amount of aparticular fuel in the engine crankcase can be determined by subtractingthe amount of that type of fuel purged from the crankcase from theamount of that type of fuel that has entered the crankcase. The totalfuel amount of a particular type of fuel in the crankcase can beexpressed as:Fuel_liq₁=Int_crk_fuel₁+Σ(Crk_cyl₁(n)−Crk_prg₁(n))where Fuel_liq represents the total amount of liquid fuel in thecrankcase, Int_crk_fuel represents the estimated amount of fuel in thecrankcase before the engine is started, Crk_cyl(n) is the amount of fuelentering the crankcase each cylinder cycle, Crk_prg(n) is the amount offuel evacuated from the crankcase each cylinder cycle and is related toor a function of the amount of fuel in vapor state Fuel_vap determinedin step 209, n is the number of cylinder cycles from engine start, andthe subscript denotes a particular fuel type (e.g., 1=gasoline;2=ethanol; 3=methanol).

If the engine is stopped before the time to fully vaporize the crankcasefuel has transpired, then the remaining individual fuel amounts can bestored in memory and used when the engine is restarted. The fuel amountsstored in memory are combined with or added to the fuel amountsestimated to entering the crankcase during the present start, therebyincreasing the estimated fuel amount in the crankcase and the purgetime. In this way, fuel that enters the crankcase over many enginestarts can be accounted for if the crankcase temperatures do not reachthe fuel vaporization temperature.

It should also be noted that for equal volumes of gasoline and ethanol,substantially all ethanol will go from a liquid state to a gaseous statewhen the boiling point of ethanol is reached and when given enough time.On the other hand, the total amount of gasoline going into vapor willgradually increase as the temperature of gasoline is increased. As such,for equal volumes of gasoline and ethanol, more ethanol vapor may bepurged from a crankcase over a shorter time interval as long as theboiling temperature of ethanol is reached.

After determining the amount of fuel in the crankcase, the routineproceeds to step 207.

At step 207, the routine determines if fuel vaporization has commenced.In one embodiment, the onset of fuel vaporization (i.e., the PCV lowervaporization temperature limit or the lower temperature limit at whichthe fuel begins to vaporize at ambient pressure) in the crankcase isrelated to engine coolant temperature or engine oil temperature. In oneexample, if the engine coolant temperature or engine oil temperatureexceeds a first predetermined value, then a particular fuel type may beconsidered to be transitioning to a vapor state. On the other hand, ifcoolant temperature is less than the predetermined amount, no orinsignificant fuel vaporization is deemed to have occurred for theparticular fuel type. In some embodiments, if coolant temperatureexceeds a second predetermined temperature (i.e., the PCV uppervaporization temperature limit or the temperature limit at which thefuel is substantially vaporized) for a predetermined amount of time thatis related to the amount of fuel in the crankcase, the strategy maydetermine that all the condensed fuel in the crankcase has beenvaporized. However, fuel in a gaseous state may continue to enter thecrankcase if it passes the piston rings.

It should also be noted that the above-mentioned lower and upper vaporlimit temperatures can be varied to accommodate different types of fuel.Thus, one type of fuel may be determined to begin to vaporize at anengine coolant temperature of 75° C. and be completely vaporized at 80°C. while a different type of fuel may begin to vaporize at 10° C. and becompletely vaporized at 95° C. at the same pressure.

It should also be noted that there are other methods for determining orestimating the amount of fuel in the engine crankcase. Therefore, theabove method is not intended to limit the breadth of the presentdescription, but rather as a non-limiting example.

If fuel vaporization has commenced the routine proceeds to step 209. Ifnot, the routine proceeds to step 215.

In step 209, the routine determines the effect that engine temperature,time at a temperature, fuel type, and amount of fuel in the crankcasehave on fuel vaporization within the crankcase. In one example, thesefactors may be empirically determined or determined by modeling and thenmultiplied together to form a first-order time constant that representsfuel the vaporization rate within the crankcase. The fuel in vapor statecan then be expressed as:Fuel_vap=Fuel_liq·e ^(−αt)Where Fuel_vapor is the estimated fuel mass that is in vapor state;Fuel_liq is the liquid fuel mass in the crankcase determined in step205; e is base of the natural logarithm; α is the variable determinedfrom engine temperature, effect of time at a temperature, and fuel type;and t is time since fuel is at conditions for vaporization. Of course,higher order estimates that represent vaporization rates for differenttypes of fuels may also be constructed if desired. After determining theamount of fuel in vapor the routine proceeds to step 211.

At step 211, the routine determines if it is desirable to store fuelvapors in a PCV canister.

Based on the fuel type determined in step 203, the routine can selectalternative strategies or methods to decide when to store crankcasehydrocarbons in the PCV canister.

In one embodiment, when gasoline is in the crankcase and the engine iscold started, fuel vapors are directed from the engine crankcase to thestorage media by positioning valve 71 such that PCV canister 76 is incommunication with crankcase 51 (hydrocarbon storage mode).Simultaneously, valve 72 is opened to allow a path for hydrocarbonreduced gas to pass from crankcase 51 to intake manifold 44. Thecrankcase gases are passed through PCV canister 76 until the engineair-fuel control is adjusted from sensed exhaust gases, or until apredetermined time or operating condition occurs (e.g., engine coolanttemperature or engine oil temperature reaching predeterminedconditions). After hydrocarbon storage is complete, the state of valve71 is changed so that crankcase gases can flow directly to the intakemanifold and valve 72 is closed (PCV canister bypass mode).

In another embodiment, when alcohol is in the crankcase, and the engineis cold started, valve 71 is positioned to allow communication betweencrankcase 51 and intake manifold 44. When a temperature of the engine(e.g., coolant temperature or oil temperature) reaches a predeterminedvalue, valve 71 is positioned to allow communication between crankcase51 and PCV canister 76. At this time, valve 72 is also opened to allowhydrocarbon reduced gases to flow from crankcase 51 to intake manifold44. Valve 72 is closed and valve 71 is returned to the position thatallows crankcase gases to bypass PCV canister 76 when engine temperaturereaches a second temperature or after a predetermined amount of time.Alternatively, valves 71 and 72 can be repositioned from the hydrocarbonstorage mode to the bypass mode when a temperature of the engine reachesa predetermined temperature for a predetermined amount of time. Thepredetermined amount of time can be related to the type and estimatedamount of fuel in the crankcase.

In still another envisioned embodiment, the routine uses a plurality ofparameters including, but not limited to coolant temperature, time sincestart, amount of fuel in the crankcase, and the amount of stored fuelvapor to determine when to store crankcase vapors to the PCV canister.

If conditions are met to store vapors to a PCV canister the routineproceeds to step 213. If not, the routine proceeds to step 215.

In step 213, the routine commands selected control valves in a mannerthat will cause crankcase fuel vapors to be stored in a canister.

In one embodiment, valves are commanded as described in step 211. Thisis accomplished by way of two-way valve 71 and one-way valve 72.

In another embodiment, two-way valve 71 is replaced by two one-wayvalves and the valves are commanded to store crankcase hydrocarbons incanister 76. After the canister control valves are operated the routinereturns to step 211.

At step 215, the routine determines whether engine operating conditionsare desirable for combusting stored fuel vapors. In one embodiment,canister purge is permitted after a plurality of engine operatingconditions have been met, the conditions including but not limited tothe engine exceeding a predetermined coolant temperature, apredetermined period of time since engine start has been exceeded, andthe engine being within a prescribed speed and load region. In otherembodiments, fewer engine conditions may be required to purge thecanister. For example, the canister may be purged when the engine isoperated at higher loads so that the fraction of combusted hydrocarbonsoriginating from the canister is low as compared to the amount of fuelbeing injected. In another embodiment, canister purge is permitted afterthe engine coolant temperature reaches a predetermined temperature.

Once started, the canister purging process can continue until theexhaust gas oxygen sensor detects little or no hydrocarbons related tothe crankcase or until other engine operating conditions indicated thatcanister purging should be inhibited. For example, crankcase purging canbe stopped if sensors detect no change in exhaust gas hydrocarbons whenthe flow of crankcase gases is cycled on and off. In another example,crankcase purging can be deactivated when the engine shuts off fuelduring deceleration or when engine load is less than a predeterminedamount.

If the engine operating conditions have been met for combusting storedhydrocarbons the routine proceeds to step 217. Otherwise, the canisterflow control valves are closed and the routine proceeds to exit.

At step 217, the routine releases fuel trapped in a canister into theengine intake manifold. In the embodiment shown in FIG. 1, the canisteris purged when two-way valve 71 is positioned such that crankcase vaporsflow from the crankcase to the intake manifold. At the same time, valve72 is opened to allow fuel vapors from the canister to enter the intakemanifold. In addition, valve 73 is opened to allow heated fresh air toflow through canister 76. The heated air strips fuel from the canistermedia and the enriched air enters the intake manifold via valve 72. Theair may be heated from engine heat or by other known methods. Valve 72may also be modulated so as to control the release of canister vaporinto intake manifold 44. In one embodiment, a pulsewidth modulatedcontrol signal is sent to valve 72 to control the average position ofvalve 72. Since the air enters canister 76 from upstream of throttle 62,and since pressure in intake manifold 44 may be lower than pressureupstream of throttle 62, a pressure differential causes enriched air toflow from upstream throttle 62 to intake manifold 44.

In an alternative embodiment, the canister may be purged using heatedcrankcase gases. That is, valve 71 is positioned such that crankcasegases flow into the canister and valve 72 is opened so that gases movethrough the canister and are discharged to intake manifold 44. Usingcrankcase gases to purge the canister may be a more cost effective wayto purge the canister because valve 73 and heat exchanger 46 may beeliminated from the system for some engine configurations.

In another alternative embodiment, a compressor may be located upstreamof throttle 62. In this embodiment, positive pressure created by thecompressor can be used to pressurize canister 76 and cause fuel vaporsto enter intake manifold 44. Thus, fuel vapors can be pushed or pulledthrough canister 76 into intake manifold 44 to facilitate purging ofstored hydrocarbons from canister 76.

As mentioned above, valve 72 can be modulated to control the flow ofenriched air from canister 76 to intake manifold 44. In one embodiment,the duty cycle of valve 72 is controlled in response to engine speed,engine load, the amount of fuel stored in the vapor canister, and sensedoxygen in exhaust gases. A three dimensional table is indexed by enginespeed, engine load, and estimated stored hydrocarbons. The duty cycle ofthe canister flow control valve (e.g., valve 72 in FIG. 1) is increased(average valve opening is increased) as engine speed and engine loadincrease. Valve opening amount is decreased when the amount ofhydrocarbons stored in the canister is high and engine speed and loadare low. Further, the valve opening amount is increased when the amountof hydrocarbons stored in the canister is low and engine speed and loadare low. Oxygen sensor feedback may also be used to adjust the canisterflow control valve duty cycle. If oxygen is detected in the exhaust gasat a higher concentration than is expected, the canister purge valveaverage opening amount can be increased while the throttle opening isreduced. The throttle opening amount is reduced in proportion to theincrease in the canister flow control valve opening amount. Likewise, ifoxygen detected in the exhaust gas is at a lower concentration than isexpected, the average canister purge valve opening amount can be reducedwhile the throttle position is substantially maintained.

In another embodiment, fuel injection timing can be adjusted when thePCV canister is purged so that the engine delivers the desired amount offuel. In particular, the amount of injected fuel is decreased by theamount of fuel estimated to enter the engine by way of the PCV canister.Further, the fuel injection amount can be increased or decreased as theoxygen concentration in the exhaust varies. Thus, the system cancompensate for the release of PCV hydrocarbons by adjusting fuelinjection timing.

After the canister flow control valves are positioned routine returns tostep 215.

Referring now to FIG. 3, an example PCV purge cycle is shown. Plots ofengine speed, engine load, engine coolant temperature, and closed-loopfuel flag are used to illustrate an example PCV canister purge sequence.The sequence begins on the left and proceeds to the right. The plots ofFIG. 3 are used to illustrate several different PCV canister purgingcycles that are related to different fuel types.

When fuels comprised of more than a predetermined amount of gasoline arein the crankcase (e.g., 80%), the PCV canister is filled and purged suchthat hydrocarbons liberated from the crankcase over a wide temperaturerange are advantageously combusted by the engine. In one embodiment, PCVcanister valves are operated so that crankcase hydrocarbons are storedin the PCV canister from engine crank until vertical marker 301 isreached. In one example, where PCV canister control valves areconfigured as illustrated in FIG. 1, valve 71 opens to allow gases toflow from crankcase 51 to canister 76. And valve 72 is opened to allowgas to exit PCV canister 76. Vertical marker 301 indicates the time atwhich the engine goes into closed-loop fuel control. In anotherembodiment, the PCV canister valves are operated so that crankcasehydrocarbons are stored in the PCV canister from engine crank until apredetermined temperature of the engine is reached at vertical marker303.

Hydrocarbons may be released from the PCV canister at different timesdepending on engine operating conditions and control objectives. Ifcrankcase hydrocarbons are stored until the engine goes closed-loop, thePCV canister contents can be purged to the engine intake system afterclosed-loop fuel control is initiated at vertical marker 301.Alternatively, the PCV canister contents can be purged to the engineintake system after the engine temperature meets a predeterminedtemperature at vertical marker 303. On the other hand, if crankcasehydrocarbons are stored until an engine temperature meets apredetermined temperature at vertical marker 303, then the PCV canistercontents can be purged to the intake manifold after the enginetemperature meets the predetermined operating temperature. In oneexample, where PCV canister control valves are configured as illustratedin FIG. 1, valve 71 changes position to allow gases to flow fromcrankcase 51 to intake manifold 44. Valves 72 and 73 are opened to allowheated intake air to purge hydrocarbon vapors from canister 76 to intakemanifold 44. In an alternate embodiment, valve 71 can continue to letcrankcase gases pass through canister 76 so that heated crankcase gaseswill cause hydrocarbons to exit canister 76 and enter intake manifold44.

PCV canister purge continues from vertical marker 301 or 303 until theengine control strategy detects a reduction of hydrocarbons beingadmitted from the PCV canister or until vertical marker 305 is reached.Marker 305 indicates that the engine is operating at a low loadcondition where it can be more difficult to control the engine air-fuelratio. Temporarily deactivating the PCV purge at vertical marker 305 canimprove engine emissions because it can be easier to control engineair-fuel by using fuel injectors rather than using PCV canisterhydrocarbon release estimates. PCV canister purge remains deactivatedwhile the engine is at low load conditions. In one embodiment, PCVcanister purge can be deactivated by closing valves 71, 72, and 73.

It should be noted that the system configuration illustrated in FIG. 1allows crankcase gases to bypass the PCV canister when crankcasehydrocarbons are not being stored to the PCV canister. Thus, the systemof FIG. 1 can use heated fresh air that is routed through valve 73 andpassed through PCV canister 76 and valve 72 to purge the PCV canisterwhile crankcase gases are ingested to the engine via two-way valve 71.

At vertical marker 307, engine load increases and PCV canister purgeresumes until the engine control system strategy detects a reduction ofhydrocarbons being admitted from the PCV canister or until low engineload conditions are reached.

When fuels comprised of more than a predetermined amount of alcohol arein the crankcase (e.g., 50%), the PCV canister is filled and purged suchthat hydrocarbons liberated from the crankcase over a narrowertemperature range are advantageously combusted by the engine. In oneembodiment, PCV canister valves are operated so that crankcasehydrocarbons bypass the PCV canister from engine crank until verticalmarker 303 is reached. That is, hydrocarbons are not store to the PCVcanister until a predetermined temperature of the engine is reached. Inone embodiment, where PCV control valves are configured as illustratedin FIG. 1. The PCV canister is bypassed by setting two-way valve 71 suchthat crankcase gases to flow from crankcase 51 to intake manifold 44.During PCV bypass, valves 72 and 73 are put in the closed position.

Hydrocarbons are stored in the PCV canister from vertical 303 untilvertical marker 305. Hydrocarbons are stored by positioning valve 71such that gases flow from crankcase 51 to canister 76. Valve 72 is alsoopened to provide a path for gases to flow from canister 76 to intakemanifold 44. Vertical marker 305 in this example indicates twoconditions: a low engine load condition and a second predeterminedengine temperature. If hydrocarbons are being stored in the PCV canisterand if the engine temperature meets or exceeds a predeterminedtemperature, the PCV canister filling operation can be stopped and thePCV canister contents purged to the engine intake system. On the otherhand, if a low engine load is reached while the PCV canister is beingfilled the PCV canister can continue to fill or filling may bedeactivated without purging the PCV canister until a higher engine loadis achieved.

At vertical marker 307, engine load increases and PCV canister purgebegins purging until the engine control system strategy detects areduction of hydrocarbons being admitted from the PCV canister or untillow engine load conditions are reached. Purge is initiated in theconfiguration illustrated in FIG. 1 by setting valve 71 to a positionwhere crankcase gases are routed to the intake manifold. In addition,valves 72 and 73 are set to the open position so that heated fresh airis routed through PCV canister 76. In an alternative embodiment, the PCVcanister can be purged by setting valve 71 such that crankcase gases canflow from crankcase 41 to PCV canister 76 while valve 72 is open. Valve73 is not required if PCV purging is performed using crankcase gases.

When fuels comprised of a predetermined mixture range of alcohol andgasoline are in the crankcase (e.g., fuels between 49% and 80%gasoline), the PCV canister is filled and purged such that hydrocarbonsliberated from the crankcase are advantageously combusted by the engine.In one embodiment, PCV canister valves are operated so that crankcasehydrocarbons are stored in the PCV canister from engine crank untilvertical marker 301 is reached.

Hydrocarbons stored in the PCV canister are then purged to the engineintake system from vertical 301 until vertical marker 303. At verticalmarker 303, hydrocarbons are stored again. In this embodiment, verticalmarker 303 corresponds to a predetermined temperature of the engine. Andthe predetermined temperature of the engine is related to the boilingpoint of a single boiling point fuel (e.g., ethanol). Crankcasehydrocarbons are stored to the PCV canister when the engine reaches thepredetermined temperature that is related to the boiling point of thesingle boiling point fuel.

In this embodiment, vertical marker 305 also indicates two conditions: alow engine load condition and a second predetermined engine temperature.If hydrocarbons are being stored in the PCV canister and the enginemeets or exceeds a predetermined temperature the PCV canister fillingoperation can be stopped and the PCV canister contents purged to theengine intake system. On the other hand, if a low engine load is reachedwhile the PCV canister is being filled the PCV canister can continue tofill or filling may be deactivated without purging the PCV canisteruntil a higher engine load is achieved.

At vertical marker 307, engine load increases and the PCV canister purgecycle begins. Purging continues until the engine control system strategydetects a reduction of hydrocarbons being admitted from the PCV canisteror until low engine load conditions are reached.

The methods, routines, and configurations disclosed herein are exemplaryand should not be considered limiting because numerous variations arepossible. For example, the above disclosure may be applied to I3, I4,I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline,diesel, or alternative fuel configurations.

The following claims point out certain combinations regarded as noveland nonobvious. Certain claims may refer to “an” element or “a first”element or equivalent. However, such claims should be understood toinclude incorporation of one or more elements, neither requiring norexcluding two or more such elements. Other variations or combinations ofclaims may be claimed through amendment of the present claims or throughpresentation of new claims in a related application. The subject matterof these claims should be regarded as being included within the subjectmatter of the present disclosure.

1. A method for processing gases from a crankcase of an engine,comprising: purging gases from the crankcase to an intake whilebypassing a canister for a first duration; then storing gases from thecrankcase in the canister for a second duration; then purging the storedgases from the canister for a third duration; and deliveringexhaust-heated fresh air to the canister during the third duration. 2.The method of claim 1 further comprising moving the gases from thecrankcase during predetermined engine operating conditions.
 3. Themethod of claim 2 wherein the predetermined engine operating conditionscomprise a temperature of the engine.
 4. The method of claim 3 whereinthe temperature of the engine is a coolant or oil temperature.
 5. Themethod of claim 1 further comprising moving the gases from the crankcaseto the intake while purging the stored gases from the canister.
 6. Themethod of claim 1 wherein an amount of fuel delivered to the engine byfuel injection is decreased when purging the stored gases from thecanister.
 7. The method of claim 1 wherein a controller adjusts anaverage position of a valve during a time interval to regulate flow ofgases from the canister to the engine.
 8. The method of claim 1 furthercomprising adjusting a position of a valve to control a purge rate ofgases from the canister; and combusting the purged gases in the engine.9. A method for processing gases from a crankcase of an enginecomprising: purging gases from the crankcase to an intake whilebypassing a canister for a first duration; then storing gases from thecrankcase in the canister for a second duration; then purging the storedgases from the canister for a third duration, wherein one or more of thefirst, second, and third durations are based on a fuel alcohol content.10. The method of claim 1 wherein purge gases from the canister areintroduced to the engine downstream of an intake throttle.
 11. A methodfor processing gases from a crankcase of an engine, comprising: purginggases from the crankcase to an intake while bypassing a canister for afirst duration; then storing gases from the crankcase in the canisterfor a second duration; then purging the stored gases from the canisterfor a third duration, wherein purge gases from the canister areintroduced to the engine downstream of an intake throttle, and whereinfresh air from upstream of the intake throttle is routed through thecanister to purge the canister.